1. Technical Field
The disclosure relates to a processing apparatus, an endoscope system, an endoscope apparatus, a method for operating an image processing apparatus, and a computer-readable recording medium, for processing an image signal captured by imaging a biological tissue.
2. Related Art
As a known art in the medical field, an endoscope system is used for observing internal portions of a subject. Typically in the endoscope system, a flexible elongated insertion unit is configured to be inserted into a subject such as a patient, white light as illumination light is emitted from a distal end of the insertion unit, and an imaging unit provided at the distal end of the insertion unit receives reflected light of the white light, thereby to capture an in-vivo image. A biological image captured in this manner is displayed on a display of the endoscope system.
In endoscopic fields in recent years, an endoscope system has appeared that irradiates a biological tissue with excitation light (e.g. blue light) other than white light via an insertion unit inserted into a subject, and receives, by an imaging unit, green autofluorescence emitted from the biological tissue in response to the excitation light, thereby obtaining a fluorescence image signal of the biological tissue (see JP 3285265 B2, for example). This technique utilizes a fact that autofluorescence intensity is weak in an abnormal site such as a lesion site compared with a normal site, and obtains a fluorescence image signal of green autofluorescence emitted from the biological tissue by irradiation with the excitation light. Further in this technique, with a frame different from the fluorescence image signal, an image signal corresponding to reflected light from the biological tissue when irradiated with the green light is obtained as a reference image signal including no autofluorescence of the abnormal site. The reference image signal is then subtracted from the fluorescence image signal to generate a fluorescence differential image signal in which the abnormal site is highlighted and displayed.